1. Field of the Invention
The present invention relates to a method for manufacturing organic solar cells, in particular to a method for manufacturing organic solar cells via a large-area manufacturing method, such as spraying, roll-to-roll web-coating, printing or similar methods, and a method for modifying morphology of an active layer by hot solvent vapor annealing manufacturing process.
2. Description of the Related Art
A research in solar cells is an expectant direction of the renewable energy sources. Although most of the commercialized products utilize the silicon as their main material, the organic solar cells still attract the attention of the industrial and academic fields due to the simple manufacturing procedure, the low manufacturing cost, the light material, and the flexibility.
While manufacturing the organic solar cell, an active layer of the solar cell is manufactured by spin coating which renders the layer provide a better flatness and uniformity. However, the spin coating is restricted by being unable to be applied in the manufacture of the solar cell with a large area but a small area, so that an innate choke point is existed in the consideration of reducing the cost in the future commercialization. Therefore, other large-area proceeding methods, such as spray coating or roll-to-roll coating, are considered in the large-area manufacture of the organic solar cells.
However, while manufacturing an active layer of the organic solar cell by spraying, knife coating, roll-to-roll web-coating, dip coating, or printing method, such as ink-jet printing, screen printing, and lithographing, the flatness and uniformity of the layer hardly attain a quality of film manufactured by the present spin coating process, and the thickness of the layer is thicker. Further, a morphology of the active layer, which includes the flatness and uniformity of the layer, and the thickness of the active layer have an important effect on a power conversion efficiency of the entire elements. Therefore, in the organic solar cell manufactured by a large-area production, it is necessary to modify the active layer.
Referring to Taiwan patent number TW 1369011, by “tandem organic solar cell”, is disclosed. The prior patent discloses an active layer manufactured by spin coating, bar coating, dip coating, roll coating, spray coating, gravure coating, ink-jet printing, slot coating, or knife coating. However, the prior patent does not disclose a technological method of utilizing the above-mentioned methods to improve the morphology of active layer with a large area, which may reduce the efficiency if adopting this process.
Referring to Taiwan publication number TW 201302839, by “organic semiconductor compositions”, is disclosed. This prior patent discloses manufacturing methods of the active layer including spin coating, knife coating, roll-to-roll web-coating, dip coating, and many kinds of printing methods, such as ink jet printing, screen printing, and lithographing. Wherein, after removing a required quantity of a solvent to forma semiconductor layer, the semiconductor layer can be annealed by being exposed to heat or solvent vapor. However, the conventional solvent annealing disclosed in this prior patent is annealed under a room temperature, so the proceeding time usually takes more than 60 minutes, and the efficiency of improving the elements is also not obvious.
Referring to the United States of America patent number US 20110008926, this prior patent also discloses an active layer which adopts the conventional solvent annealing process while spraying and has the same defect as the above-mentioned patent.
Referring to Taiwan patent number TW 201139503, by “copolymer semiconductors comprising thiazolothiazole or benzobisthiazole, or benzobisoxazole electron acceptor subunits, and electron donor subunits, and their uses in transistors and solar cells”, is disclosed. While an active layer is manufactured, a solvent is freely heated so as to enlarge dissolution of the copolymer and/or the electron acceptor for assisting a formation of the layer. The above-mentioned process is processed before forming the active layer, and the structure and morphology of the layer are not modified after the active layer is formed, which will meet an unevenness of the active layer while applying to a large-area production of the organic solar cells, thereby causing a decrease of the element efficiency.